This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. AIMS: Methamphetamine (METH) use increased 60 percent in 2009, even though users are at high risk for addiction, neurotoxicity and cognitive impairment. As adolescents are more susceptible to METH addiction and other these adverse consequences than adults, we hypothesized that METH affects behaviors and neurodevelopmental genes (axonal guidance molecules or AGMs) differently in adolescent and adults. We investigated the effects of METH on expression of genes implicated in neurodevelopment, neurogenesis, neuroadaptation in adolescent and adult brain. METHODS: We compared METH (5 mg/kg) with saline in 12 adolescent male (30 days) and 12 adult male mice (10 weeks), given i.p. daily for 6 days, by measuring locomotor activity, stereotypy and mRNA expression of AGMs in 3 brain regions. RESULTS: METH (5 mg/kg) increased locomotor activity in adolescent and adult mice, but in the adolescent mice: (1) peak effects were later;(2) locomotion was higher;(3) duration was longer. In the two age cohorts, expression levels of specific AGMs differed following METH treatment in hippocampus and striatum. CONCLUSIONS: METH affected locomotion and AGM gene expression differently in adolescent and adult mice. Altered mRNA expression levels of specific AGMs in hippocampus, striatum conceivably are associated with the cascade of METH-induced neurodevelopmental, morphological, behavioral, cognitive changes in brain. Combined with other strategies, this novel approach may clarify the mechanisms by which METH confers heightened susceptibility of the adolescent to addiction and to other adverse consequences.